Electrically variable transmission having two planetary gear sets with one fixed interconnection

ABSTRACT

The electrically variable transmission family of the present invention provides low-content, low-cost electrically variable transmission mechanisms including first and second differential gear sets, a battery, two electric machines serving interchangeably as motors or generators, and four or five selectable torque-transfer devices. The selectable torque transfer devices are engaged singly or in combinations of two to yield an EVT with a continuously variable range of speeds (including reverse) and four mechanically fixed forward speed ratios. The torque transfer devices and the first and second motor/generators are operable to provide five operating modes in the electrically variable transmission, including battery reverse mode, EVT reverse mode, reverse and forward launch modes, continuously variable transmission range mode, and fixed ratio mode.

TECHNICAL FIELD

The present invention relates to electrically variable transmissionswith selective operation both in power-split variable speed ratio rangesand in fixed speed ratios, and having two planetary gear sets, twomotor/generators and four or five torque transmitting mechanisms.

BACKGROUND OF THE INVENTION

Internal combustion engines, particularly those of the reciprocatingpiston type, currently propel most vehicles. Such engines are relativelyefficient, compact, lightweight, and inexpensive mechanisms by which toconvert highly concentrated energy in the form of fuel into usefulmechanical power. A novel transmission system, which can be used withinternal combustion engines and which can reduce fuel consumption andthe emissions of pollutants, may be of great benefit to the public.

The wide variation in the demands that vehicles typically place oninternal combustion engines increases fuel consumption and emissionsbeyond the ideal case for such engines. Typically, a vehicle ispropelled by such an engine, which is started from a cold state by asmall electric motor and relatively small electric storage batteries,then quickly placed under the loads from propulsion and accessoryequipment. Such an engine is also operated through a wide range ofspeeds and a wide range of loads and typically at an average ofapproximately a fifth of its maximum power output.

A vehicle transmission typically delivers mechanical power from anengine to the remainder of a drive system, such as fixed final drivegearing, axles and wheels. A typical mechanical transmission allows somefreedom in engine operation, usually through alternate selection of fiveor six different drive ratios, a neutral selection that allows theengine to operate accessories with the vehicle stationary, and clutchesor a torque converter for smooth transitions between driving ratios andto start the vehicle from rest with the engine turning. Transmissiongear selection typically allows power from the engine to be delivered tothe rest of the drive system with a ratio of torque multiplication andspeed reduction, with a ratio of torque reduction and speedmultiplication known as overdrive, or with a reverse ratio.

An electric generator can transform mechanical power from the engineinto electrical power, and an electric motor can transform that electricpower back into mechanical power at different torques and speeds for theremainder of the vehicle drive system. This arrangement allows acontinuous variation in the ratio of torque and speed between engine andthe remainder of the drive system, within the limits of the electricmachinery. An electric storage battery used as a source of power forpropulsion may be added to this arrangement, forming a series hybridelectric drive system.

The series hybrid system allows the engine to operate with someindependence from the torque, speed and power required to propel avehicle, so the engine may be controlled for improved emissions andefficiency. This system allows the electric machine attached to theengine to act as a motor to start the engine. This system also allowsthe electric machine attached to the remainder of the drive train to actas a generator, recovering energy from slowing the vehicle into thebattery by regenerative braking. A series electric drive suffers fromthe weight and cost of sufficient electric machinery to transform all ofthe engine power from mechanical to electrical in the generator and fromelectrical to mechanical in the drive motor, and from the useful energylost in these conversions.

A power-split transmission can use what is commonly understood to be“differential gearing” to achieve a continuously variable torque andspeed ratio between input and output. An electrically variabletransmission can use differential gearing to send a fraction of itstransmitted power through a pair of electric motor/generators. Theremainder of its power flows through another, parallel path that is allmechanical and direct, of fixed ratio, or alternatively selectable.

One form of differential gearing, as is well known to those skilled inthis art, may constitute a planetary gear set. Planetary gearing isusually the preferred embodiment employed in differentially gearedinventions, with the advantages of compactness and different torque andspeed ratios among all members of the planetary gear set. However, it ispossible to construct this invention without planetary gears, as byusing bevel gears or other gears in an arrangement where the rotationalspeed of at least one element of a gear set is always a weighted averageof speeds of two other elements.

A hybrid electric vehicle transmission system also includes one or moreelectric energy storage devices. The typical device is a chemicalelectric storage battery, but capacitive or mechanical devices, such asan electrically driven flywheel, may also be included. Electric energystorage allows the mechanical output power from the transmission systemto the vehicle to vary from the mechanical input power from the engineto the transmission system. The battery or other device also allows forengine starting with the transmission system and for regenerativevehicle braking.

An electrically variable transmission in a vehicle can simply transmitmechanical power from an engine input to a final drive output. To do so,the electric power produced by one motor/generator balances theelectrical losses and the electric power consumed by the othermotor/generator. By using the above-referenced electrical storagebattery, the electric power generated by one motor/generator can begreater than or less than the electric power consumed by the other.Electric power from the battery can sometimes allow bothmotor/generators to act as motors, especially to assist the engine withvehicle acceleration. Both motors can sometimes act as generators torecharge the battery, especially in regenerative vehicle braking.

A successful substitute for the series hybrid transmission is thetwo-range, input-split and compound-split electrically variabletransmission now produced for transit buses, as disclosed in U.S. Pat.No. 5,931,757, issued Aug. 3, 1999, to Michael Roland Schmidt, commonlyassigned with the present application, and hereby incorporated byreference in its entirety. Such a transmission utilizes an input meansto receive power from the vehicle engine and a power output means todeliver power to drive the vehicle. First and second motor/generatorsare connected to an energy storage device, such as a battery, so thatthe energy storage device can accept power from, and supply power to,the first and second motor/generators. A control unit regulates powerflow among the energy storage device and the motor/generators as well asbetween the first and second motor/generators.

Operation in first or second variable-speed-ratio modes of operation maybe selectively achieved by using clutches in the nature of first andsecond torque transfer devices. In the first mode, an input-power-splitspeed ratio range is formed by the application of the first clutch, andthe output speed of the transmission is proportional to the speed of onemotor/generator. In the second mode, a compound-power-split speed ratiorange is formed by the application of the second clutch, and the outputspeed of the transmission is not proportional to the speeds of either ofthe motor/generators, but is an algebraic linear combination of thespeeds of the two motor/generators. Operation at a fixed transmissionspeed ratio may be selectively achieved by the application of both ofthe clutches. Operation of the transmission in a neutral mode may beselectively achieved by releasing both clutches, decoupling the engineand both electric motor/generators from the transmission output. Thetransmission incorporates at least one mechanical point in its firstmode of operation and at least two mechanical points in its second modeof operation.

U.S. Pat. No. 6,527,658, issued Mar. 4, 2003 to Holmes et al, commonlyassigned with the present application, and hereby incorporated byreference in its entirety, discloses an electrically variabletransmission utilizing two planetary gear sets, two motor/generators andtwo clutches to provide input split, compound split, neutral and reversemodes of operation. Both planetary gear sets may be simple, or one maybe individually compounded. An electrical control member regulates powerflow among an energy storage device and the two motor/generators. Thistransmission provides two ranges or modes of electrically variabletransmission (EVT) operation, selectively providing an input-power-splitspeed ratio range and a compound-power-split speed ratio range. Onefixed speed ratio can also be selectively achieved.

SUMMARY OF THE INVENTION

The present invention provides a family of electrically variabletransmissions offering several advantages over conventional automatictransmissions for use in hybrid vehicles, including improved vehicleacceleration performance, improved fuel economy via regenerative brakingand electric-only idling and launch, and an attractive marketingfeature. An object of the invention is to provide the best possibleenergy efficiency and emissions for a given engine. In addition, optimalperformance, capacity, package size, and ratio coverage for thetransmission are sought.

The electrically variable transmission family of the present inventionprovides low-content, low-cost electrically variable transmissionmechanisms including first and second differential gear sets, a battery,two electric machines serving interchangeably as motors or generators,and four or five selectable torque-transfer devices (two clutches andtwo or three brakes). Preferably, the differential gear sets areplanetary gear sets, but other gear arrangements may be implemented,such as bevel gears or differential gearing to an offset axis.

In this description, the first and second planetary gear sets may becounted left to right or right to left.

Each of the planetary gear sets has three members. The first, second orthird member of each planetary gear set can be any one of a sun gear,ring gear or carrier.

Each carrier can be either a single-pinion carrier (simple) or adouble-pinion carrier (compound).

The input shaft is continuously connected with at least one member ofthe planetary gear sets. The output shaft is continuously connected withanother member of the planetary gear sets.

An interconnecting member continuously connects a first member of thefirst planetary gear set and a first member of the second planetary gearset.

A first torque transfer device selectively connects a member of thefirst planetary gear set with another member of the first or secondplanetary gear set.

A second torque transfer device selectively connects a member of thesecond planetary gear set with another member of the first or secondplanetary gear set, this pair of members being different from the onesconnected by the first torque transfer device.

A third torque transfer device selectively connects a member of thefirst or second planetary gear set with a stationary member(transmission case).

A fourth torque transfer device is implemented as a brake connected inparallel with one of the motor/generators for braking rotation thereof.An optional fifth torque transfer device may be implemented as a brakeconnected in parallel with the other one of the motor/generators forbraking rotation thereof.

The first motor/generator is mounted to the transmission case (orground) and is continuously connected to a member of the first or secondplanetary gear set.

The second motor/generator is mounted to the transmission case and iscontinuously connected to a member of the first or second planetary gearset, this member being different from the member connected with thefirst motor/generator.

The four or five selectable torque transfer devices are engaged singlyor in combinations of two to yield an EVT with a continuously variablerange of speeds (including reverse) and four mechanically fixed forwardspeed ratios. A “fixed speed ratio” is an operating condition in whichthe mechanical power input to the transmission is transmittedmechanically to the output, and no power flow (i.e. almost zero) ispresent in the motor/generators. An electrically variable transmissionthat may selectively achieve several fixed speed ratios for operationnear full engine power can be smaller and lighter for a given maximumcapacity. Fixed ratio operation may also result in lower fuelconsumption when operating under conditions where engine speed canapproach its optimum without using the motor/generators. A variety offixed speed ratios and variable ratio spreads can be realized bysuitably selecting the tooth ratios of the planetary gear sets.

Each embodiment of the electrically variable transmission familydisclosed has an architecture in which neither the transmission inputnor output is directly connected to a motor/generator. This allows for areduction in the size and cost of the electric motor/generators requiredto achieve the desired vehicle performance.

The first, second, third and fourth (and optional fifth) torque transferdevices and the first and second motor/generators are operable toprovide five operating modes in the electrically variable transmission,including battery reverse mode, EVT reverse mode, reverse and forwardlaunch modes, continuously variable transmission range mode, and fixedratio mode.

The above features and advantages, and other features and advantages ofthe present invention are readily apparent from the following detaileddescription of the best modes for carrying out the invention when takenin connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a is a schematic representation of a powertrain including anelectrically variable transmission incorporating a family member of thepresent invention;

FIG. 1 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 1a;

FIG. 2 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 2 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 2a;

FIG. 3 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 3 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 3a;

FIG. 4 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 4 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 4a;

FIG. 5 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 5 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 5a;

FIG. 6 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 6 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 6a;

FIG. 7 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 7 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 7a;

FIG. 8 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 8 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 8a;

FIG. 9 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 9 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 9a;

FIG. 10 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 10 b is an operating mode table and fixed ratio mode tabledepicting some of the operating characteristics of the powertrain shownin FIG. 10 a;

FIG. 11 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 11 b is an operating mode table and fixed ratio mode tabledepicting some of the operating characteristics of the powertrain shownin FIG. 11 a;

FIG. 12 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 12 b is an operating mode table and fixed ratio mode tabledepicting some of the operating characteristics of the powertrain shownin FIG. 12 a;

FIG. 13 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 13 b is an operating mode table and fixed ratio mode tabledepicting some of the operating characteristics of the powertrain shownin FIG. 13 a;

FIG. 14 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention; and

FIG. 14 b is an operating mode table and fixed ratio mode tabledepicting some of the operating characteristics of the powertrain shownin FIG. 14 a.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIG. 1 a, a powertrain 10 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission (EVT), designated generally by thenumeral 14. Transmission 14 is designed to receive at least a portion ofits driving power from the engine 12. As shown, the engine 12 has anoutput shaft that serves as the input member 17 of the transmission 14.A transient torque damper (not shown) may also be implemented betweenthe engine 12 and the input member 17 of the transmission.

In the embodiment depicted the engine 12 may be a fossil fuel engine,such as a diesel engine which is readily adapted to provide itsavailable power output typically delivered at a constant number ofrevolutions per minute (RPM).

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connected to a planetary gear set 20 in the transmission 14.

An output member 19 of the transmission 14 is connected to a final drive16.

The transmission 14 utilizes two differential gear sets, preferably inthe nature of planetary gear sets 20 and 30. The planetary gear set 20employs an outer gear member 24, typically designated as the ring gear.The ring gear 24 circumscribes an inner gear member 22, typicallydesignated as the sun gear. A carrier 26 rotatably supports a pluralityof planet gears 27 such that each planet gear 27 meshingly engages boththe outer, ring gear member 24 and the inner, sun gear member 22 of thefirst planetary gear set 20. The input member 17 is secured to thecarrier 26 of the planetary gear set 20.

The planetary gear set 30 also has an outer gear member 34, often alsodesignated as the ring gear, that circumscribes an inner gear member 32,also often designated as the sun gear. A plurality of planet gears 37are also rotatably mounted in a carrier 36 such that each planet gearmember 37 simultaneously, and meshingly, engages both the outer, ringgear member 34 and the inner, sun gear member 32 of the planetary gearset 30.

An interconnecting member 70 continuously connects the ring gear 24 ofthe planetary gear set 20 with the sun gear 32 of the planetary gear set30.

The first preferred embodiment 10 also incorporates first and secondmotor/generators 80 and 82, respectively. The stator of the firstmotor/generator 80 is secured to the transmission housing 60. The rotorof the first motor/generator 80 is secured to the sun gear 22.

The stator of the second motor/generator 82 is also secured to thetransmission housing 60. The rotor of the second motor/generator 82 issecured to the ring gear 24.

A first torque transfer device, such as a clutch 50, selectivelyconnects the ring gear 24 of the planetary gear set 20 to the carrier 26of the planetary gear set 20. A second torque transfer device, such asclutch 52, selectively connects the sun gear 32 of the planetary gearset 30 with the carrier 36 of the planetary gear set 30. A third torquetransfer device, such as brake 54, selectively connects the ring gear 34of the planetary gear set 30 with the transmission housing 60. That is,the ring gear 34 is selectively secured against rotation by an operativeconnection to the non-rotatable housing 60. A fourth torque transferdevice, such as brake 55, selectively brakes the rotor of themotor/generator 80. The first, second, third and fourth torque transferdevices 50, 52, 54 and 55 are employed to assist in the selection of theoperational modes of the hybrid transmission 14, as will be hereinaftermore fully explained.

The output drive member 19 of the transmission 14 is secured to thecarrier 36 of the planetary gear set 30.

Returning now to the description of the power sources, it should beapparent from the foregoing description, and with particular referenceto FIG. 1 a, that the transmission 14 selectively receives power fromthe engine 12. The hybrid transmission also receives power from anelectric power source 86, which is operably connected to a controller88. The electric power source 86 may be one or more batteries. Otherelectric power sources, such as fuel cells, that have the ability toprovide, or store, and dispense electric power may be used in place ofbatteries without altering the concepts of the present invention.

General Operating Considerations

One of the primary control devices is a well known drive range selector(not shown) that directs an electronic control unit (the ECU 88) to configure the transmission for either the park, reverse, neutral, orforward drive range. The second and third primary control devicesconstitute an accelerator pedal (not shown) and a brake pedal (also notshown). The information obtained by the ECU from these three primarycontrol sources is designated as the “operator demand.” The ECU alsoobtains information from a plurality of sensors (input as well asoutput) as to the status of: the torque transfer devices (either appliedor released); the engine output torque; the unified battery, orbatteries, capacity level; and, the temperatures of selected vehicularcomponents. The ECU determines what is required and then manipulates theselectively operated components of, or associated with, the transmissionappropriately to respond to the operator demand.

The invention may use simple or compound planetary gear sets. In asimple planetary gear set a single set of planet gears are normallysupported for rotation on a carrier that is itself rotatable.

In a simple planetary gear set, when the sun gear is held stationary andpower is applied to the ring gear of a simple planetary gear set, theplanet gears rotate in response to the power applied to the ring gearand thus “walk” circumferentially about the fixed sun gear to effectrotation of the carrier in the same direction as the direction in whichthe ring gear is being rotated.

When any two members of a simple planetary gear set rotate in the samedirection and at the same speed, the third member is forced to turn atthe same speed, and in the same direction. For example, when the sungear and the ring gear rotate in the same direction, and at the samespeed, the planet gears do not rotate about their own axes but ratheract as wedges to lock the entire unit together to effect what is knownas direct drive. That is, the carrier rotates with the sun and ringgears.

However, when the two gear members rotate in the same direction, but atdifferent speeds, the direction in which the third gear member rotatesmay often be determined simply by visual analysis, but in manysituations the direction will not be obvious and can only be accuratelydetermined by knowing the number of teeth present on all the gearmembers of the planetary gear set.

Whenever the carrier is restrained from spinning freely, and power isapplied to either the sun gear or the ring gear, the planet gear membersact as idlers. In that way the driven member is rotated in the oppositedirection as the drive member. Thus, in many transmission arrangementswhen the reverse drive range is selected, a torque transfer deviceserving as a brake is actuated frictionally to engage the carrier andthereby restrain it against rotation so that power applied to the sungear will turn the ring gear in the opposite direction. Thus, if thering gear is operatively connected to the drive wheels of a vehicle,such an arrangement is capable of reversing the rotational direction ofthe drive wheels, and thereby reversing the direction of the vehicleitself.

In a simple set of planetary gears, if any two rotational speeds of thesun gear, the planet carrier, and the ring gear are known, then thespeed of the third member can be determined using a simple rule. Therotational speed of the carrier is always proportional to the speeds ofthe sun and the ring, weighted by their respective numbers of teeth. Forexample, a ring gear may have twice as many teeth as the sun gear in thesame set. The speed of the carrier is then the sum of two-thirds thespeed of the ring gear and one-third the speed of the sun gear. If oneof these three members rotates in an opposite direction, the arithmeticsign is negative for the speed of that member in mathematicalcalculations.

The torque on the sun gear, the carrier, and the ring gear can also besimply related to one another if this is done without consideration ofthe masses of the gears, the acceleration of the gears, or frictionwithin the gear set, all of which have a relatively minor influence in awell designed transmission. The torque applied to the sun gear of asimple planetary gear set must balance the torque applied to the ringgear, in proportion to the number of teeth on each of these gears. Forexample, the torque applied to a ring gear with twice as many teeth asthe sun gear in that set must be twice that applied to the sun gear, andmust be applied in the same direction. The torque applied to the carriermust be equal in magnitude and opposite in direction to the sum of thetorque on the sun gear and the torque on the ring gear.

In a compound planetary gear set, the utilization of inner and outersets of planet gears effects an exchange in the roles of the ring gearand the planet carrier in comparison to a simple planetary gear set. Forinstance, if the sun gear is held stationary, the planet carrier willrotate in the same direction as the ring gear, but the planet carrierwith inner and outer sets of planet gears will travel faster than thering gear, rather than slower.

In a compound planetary gear set having meshing inner and outer sets ofplanet gears the speed of the ring gear is proportional to the speeds ofthe sun gear and the planet carrier, weighted by the number of teeth onthe sun gear and the number of teeth filled by the planet gears,respectively. For example, the difference between the ring and the sunfilled by the planet gears might be as many teeth as are on the sun gearin the same set. In that situation the speed of the ring gear would bethe sum of two-thirds the speed of the carrier and one third the speedof the sun. If the sun gear or the planet carrier rotates in an oppositedirection, the arithmetic sign is negative for that speed inmathematical calculations.

If the sun gear were to be held stationary, then a carrier with innerand outer sets of planet gears will turn in the same direction as therotating ring gear of that set. On the other hand, if the sun gear wereto be held stationary and the carrier were to be driven, then planetgears in the inner set that engage the sun gear roll, or “walk,” alongthe sun gear, turning in the same direction that the carrier isrotating. Pinion gears in the outer set that mesh with pinion gears inthe inner set will turn in the opposite direction, thus forcing ameshing ring gear in the opposite direction, but only with respect tothe planet gears with which the ring gear is meshingly engaged. Theplanet gears in the outer set are being carried along in the directionof the carrier. The effect of the rotation of the pinion gears in theouter set on their own axis and the greater effect of the orbital motionof the planet gears in the outer set due to the motion of the carrierare combined, so the ring rotates in the same direction as the carrier,but not as fast as the carrier.

If the carrier in such a compound planetary gear set were to be heldstationary and the sun gear were to be rotated, then the ring gear willrotate with less speed and in the same direction as the sun gear. If thering gear of a simple planetary gear set is held stationary and the sungear is rotated, then the carrier supporting a single set of planetgears will rotate with less speed and in the same direction as the sungear. Thus, one can readily observe the exchange in roles between thecarrier and the ring gear that is caused by the use of inner and outersets of planet gears which mesh with one another, in comparison with theusage of a single set of planet gears in a simple planetary gear set.

The normal action of an electrically variable transmission is totransmit mechanical power from the input to the output. As part of thistransmission action, one of its two motor/generators acts as a generatorof electrical power. The other motor/generator acts as a motor and usesthat electrical power. As the speed of the output increases from zero toa high speed, the two motor/generators 80, 82 gradually exchange rolesas generator and motor, and may do so more than once. These exchangestake place around mechanical points, where essentially all of the powerfrom input to output is transmitted mechanically and no substantialpower is transmitted electrically.

In a hybrid electrically variable transmission system, the battery 86may also supply power to the transmission or the transmission may supplypower to the battery. If the battery is supplying substantial electricpower to the transmission, such as for vehicle acceleration, then bothmotor/generators may act as motors. If the transmission is supplyingelectric power to the battery, such as for regenerative braking, bothmotor/generators may act as generators. Very near the mechanical pointsof operation, both motor/generators may also act as generators withsmall electrical power outputs, because of the electrical losses in thesystem.

Contrary to the normal action of the transmission, the transmission mayactually be used to transmit mechanical power from the output to theinput. This may be done in a vehicle to supplement the vehicle brakesand to enhance or to supplement regenerative braking of the vehicle,especially on long downward grades. If the power flow through thetransmission is reversed in this way, the roles of the motor/generatorswill then be reversed from those in normal action.

Specific Operating Considerations

Each of the embodiments described herein has sixteen functionalrequirements (corresponding with the 16 rows of each operating modetable shown in the Figures) which may be grouped into five operatingmodes. These five operating modes are described below and may be bestunderstood by referring to the respective operating mode tableaccompanying each transmission stick diagram, such as the operating modetables of FIG. 1 b, 2 b, 3 b, etc.

The first operating mode is the “battery reverse mode” which correspondswith the first row (Batt Rev) of each operating mode table, such as thatof FIG. 1 b. In this mode, the engine is off and the transmissionelement connected to the engine is not controlled by engine torque,though there may be some residual torque due to the rotational inertiaof the engine. The EVT is driven by one of the motor/generators usingenergy from the battery, causing the vehicle to move in reverse.Depending on the kinematic configuration, the other/motor/generator mayor may not rotate in this mode, and may or may not transmit torque. Ifit does rotate, it is used to generate energy which is stored in thebattery. In the embodiment of FIG. 1 b, in the battery reverse mode, thebrake 54 is engaged, the motor/generator 80 has zero torque, themotor/generator 82 has a torque of −1.00 units. A torque ratio of −2.78is achieved, by way of example. In each operating mode table an (M) nextto a torque value in the motor/generator columns 80 and 82 indicatesthat the motor/generator is acting as a motor, and the absence of an (M)indicates that the motor/generator is acting as generator. An “X” inthese columns illustrates that the respective motor is braked, such asby the brake 55.

The second operating mode is the “EVT reverse mode” which correspondswith the second row (EVT Rev) of each operating mode table, such as thatof FIG. 1 b. In this mode, the EVT is driven by the engine and by one ofthe motor/generators. The other motor/generator operates in generatormode and transfers 100% of the generated energy back to the drivingmotor. The net effect is to drive the vehicle in reverse. Referring toFIG. 1 b, for example, in the EVT reverse mode, the brake 54 is engaged,the generator 80 has a torque of −0.31 units, the motor 82 has a torqueof −3.69 units, and an output torque of −8.33 is achieved, correspondingto an engine torque of 1 unit.

The third operating mode includes the “reverse and forward launch modes”(also referred to as “torque converter reverse and forward modes”)corresponding with the third and fourth rows (TC Rev and TC For) of eachoperating mode table, such as that of FIG. 1 b. In this mode, the EVT isdriven by the engine and one of the motor/generators. A selectablefraction of the energy generated in the generator unit is stored in thebattery, with the remaining energy being transferred to the motor. InFIG. 1, this fraction is approximately 99%. The ratio of transmissionoutput speed to engine speed (transmission speed ratio) is approximately±0.001 (the positive sign indicates that the vehicle is creeping forwardand negative sign indicates that the vehicle is creeping backwards).Referring to FIG. 1 b, in the reverse and forward launch modes, thebrake 54 is engaged, and the motor/generator 80 acts as a generator(with −0.31 units of torque), the motor/generator 82 acts as a motor(with −3.21 or 0.99 units of torque), and a torque ratio of −7.00 or4.69 is achieved.

The fourth operating mode is a “continuously variable transmission rangemode” which includes the Range 1.1, Range 1.2, Range 1.3, Range 1.4,Range 2.1, Range 2.2, Range 2.3 and Range 2.4 operating pointscorresponding with rows 5–12 of each operating point table, such as thatof FIG. 1 b. In this mode, the EVT is driven by the engine as well asone of the motor/generators operating as a motor. The othermotor/generator operates as a generator and transfers 100% of thegenerated energy back to the motor. The operating points represented byRange 1.1, 1.2 . . . , etc. are discrete points in the continuum offorward speed ratios provided by the EVT. For example in FIG. 1 b, arange of torque ratios from 4.69 to 1.86 is achieved with the brake 54engaged, and a range of ratios 1.36 to 0.54 is achieved with the clutch52 engaged.

The fifth operating mode includes the “fixed ratio” modes (F1, F2, F3and F4) corresponding with rows 13–16 of each operating mode table (i.e.operating mode table), such as that of FIG. 1 b. In this mode thetransmission operates like a conventional automatic transmission, withtwo torque transfer devices engaged to create a discrete transmissionratio. The clutching table accompanying each figure shows only 4fixed-ratio forward speeds but additional fixed ratios may be available.Referring to FIG. 1 b, in fixed ratio F1 the clutch 50 and brake 54 areengaged to achieve a fixed torque ratio of 2.78. In fixed ratio F2, thebrakes 54 and 55 are engaged to achieve a fixed ratio of 1.94.Accordingly, each “X” in the column of motor/generator 80 in FIG. 1 bindicates that the brake 55 is engaged and the motor/generator 80 is notrotating. In fixed ratio F3, the clutches 50 and 52 are engaged toachieve a fixed ratio of 1.00. In fixed ratio F4, the clutch 52 andbrake 55 are engaged to achieve a fixed ratio of 0.70.

The transmission 14 is capable of operating in so-called single or dualmodes. In single mode, the engaged torque transfer device remains thesame for the entire continuum of forward speed ratios (represented bythe discrete points: Ranges 1.1, 1.2, 1.3 and 1.4). In dual mode, theengaged torque transfer device is switched at some intermediate speedratio (e.g., Range 2.1 in FIG. 1). Depending on the mechanicalconfiguration, this change in torque transfer device engagement hasadvantages in reducing element speeds in the transmission.

In some designs, it is possible to synchronize clutch element slipspeeds such that shifts are achievable with minimal torque disturbance(so-called “cold” shifts). For example, the transmissions of FIGS. 3 a,4 a, 5 a and 7 a have cold shifts between ranges 1.4 and 2.1. This alsoserves as an enabler for superior control during double transitionshifts (two oncoming clutches and two off-going clutches).

As set forth above, the engagement schedule for the torque transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 1 b. FIG. 1 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 1 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 20 and the N_(R2)/N_(S2) value is the tooth ratio ofthe planetary gear set 30. Also, the chart of FIG. 1 b describes theratio steps that are attained utilizing the sample of tooth ratiosgiven. For example, the step ratio between first and second fixedforward torque ratios is 1.43, the step ratio between the second andthird fixed forward torque ratios is 1.94, the step ratio between thesecond and third fixed forward torque ratios is 1.43, and the ratiospread is 3.97.

Description of a Second Exemplary Embodiment

With reference to FIG. 2 a, a powertrain 110 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral114. Transmission 114 is designed to receive at least a portion of itsdriving power from the engine 12.

In the embodiment depicted the engine 12 may also be a fossil fuelengine, such as a diesel engine which is readily adapted to provide itsavailable power output typically delivered at a constant number ofrevolutions per minute (RPM). As shown, the engine 12 has an outputshaft that serves as the input member 17 of the transmission 14. Atransient torque damper (not shown) may also be implemented between theengine 12 and the input member 17 of the transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connected to a planetary gear set in the transmission 114.An output member 19 of the transmission 114 is connected to a finaldrive 16.

The transmission 114 utilizes two differential gear sets, preferably inthe nature of planetary gear sets 120 and 130. The planetary gear set120 employs an outer gear member 124, typically designated as the ringgear. The ring gear 124 circumscribes an inner gear member 122,typically designated as the sun gear. A carrier 126 rotatably supports aplurality of planet gears 127 such that each planet gear 127 meshinglyengages both the outer, ring gear 124 and the inner, sun gear member 122of the first planetary gear set 120.

The planetary gear set 130 also has an outer gear member 134, often alsodesignated as the ring gear, that circumscribes an inner gear member132, also often designated as the sun gear. A plurality of planet gears137 are also rotatably mounted in a carrier 136 such that each planetgear member 137 simultaneously, and meshingly, engages both the outer,ring gear 134 and the inner, sun gear member 132 of the planetary gearset 130.

The transmission input member 17 is connected with the carrier 126 ofthe planetary gear set 120, and the transmission output member 19 isconnected with the carrier 136 of the planetary gear set 130. Aninterconnecting member 170 continuously connects the ring gear 124 ofthe planetary gear set 120 with the sun gear 132 of the planetary gearset 130.

The transmission 114 also incorporates first and second motor/generators180 and 182, respectively. The stator of the first motor/generator 180is secured to the transmission housing 160. The rotor of the firstmotor/generator 180 is secured to the sun gear 122 of the planetary gearset 120.

The stator of the second motor/generator 182 is also secured to thetransmission housing 160. The rotor of the second motor/generator 182 issecured to the ring gear member 124.

A first torque transfer device, such as a clutch 150, selectivelyconnects the carrier 126 of the planetary gear set 120 to the sun gear122 of the planetary gear set 120. A second torque transfer device, suchas clutch 152, selectively connects the carrier 126 of the planetarygear set 120 with the ring gear 134 of the planetary gear set 130. Athird torque transfer device, such as brake 154, selectively connectsthe ring gear 134 of the planetary gear set 130 with the transmissionhousing 160. That is, the ring gear 134 is selectively secured againstrotation by an operative connection to the non-rotatable housing 160. Afourth torque transfer device, such as the brake 155, is connected inparallel with the motor/generator 180 for selectively braking rotationof the motor/generator 180. The first, second, third and fourth torquetransfer devices 150, 152, 154 and 155 are employed to assist in theselection of the operational modes of the hybrid transmission 114.

Returning now to the description of the power sources, it should beapparent from the foregoing description, and with particular referenceto FIG. 2 a, that the transmission 114 selectively receives power fromthe engine 12. The hybrid transmission also exchanges power with anelectric power source 186, which is operably connected to a controller188. The electric power source 186 may be one or more batteries. Otherelectric power sources, such as fuel cells, that have the ability toprovide, or store, and dispense electric power may be used in place ofbatteries without altering the concepts of the present invention.

As described previously, each embodiment has sixteen functionalrequirements (corresponding with the 16 rows of each operating modetable shown in the Figures) which may be grouped into five operatingmodes. The first operating mode is the “battery reverse mode” whichcorresponds with the first row (Batt Rev) of the operating mode table ofFIG. 2 b. In this mode, the engine is off and the transmission elementconnected to the engine is effectively allowed to freewheel, subject toengine inertia torque. The EVT is driven by one of the motor/generatorsusing energy from the battery, causing the vehicle to move in reverse.The other motor/generator may or may not rotate in this mode. As shownin FIG. 2 b, in this mode the brake 154 is engaged, the motor/generator180 has zero torque, the motor 182 has a torque of −1.00 unit and anoutput torque of −2.78 is achieved, by way of example.

The second operating mode is the “EVT reverse mode” which correspondswith the second row (EVT Rev) of the operating mode table of FIG. 2 b.In this mode, the EVT is driven by the engine and by one of themotor/generators. The other motor/generator operates in generator modeand transfers 100% of the generated energy back to the driving motor.The net effect is to drive the vehicle in reverse. In this mode, thebrake 154 is engaged, the generator 180 has a torque of −0.36 units, themotor 182 has a torque of −3.63 units, and an output torque of −8.33 isachieved, corresponding to an input torque of 1 unit.

The third operating mode includes the “reverse and forward launch modes”corresponding with the third and fourth rows (TC Rev and TC For) of eachoperating mode table, such as that of FIG. 2 b. In this mode, the EVT isdriven by the engine and one of the motor/generators. A selectablefraction of the energy generated in the generator unit is stored in thebattery, with the remaining energy being transferred to the motor. Inthis mode, the brake 154 is engaged, and the motor/generator 180 acts asa generator (with −0.36 units of torque in reverse and forward), themotor/generator 182 acts as a motor (with −3.16 or 1.04 units oftorque), and a torque ratio of −7.00 or 4.69 is achieved. For thesetorque ratios, approximately 99% of the generator energy is stored inthe battery.

The fourth operating mode includes the “Range 1.1, Range 1.2, Range 1.3,Range 1.4, Range 2.1, Range 2.2, Range 2.3 and Range 2.4” modescorresponding with rows 5–12 of the operating mode table of FIG. 2 b. Inthis mode, the EVT is driven by the engine as well as one of themotor/generators operating as a motor. The other motor/generatoroperates as a generator and transfers 100% of the generated energy backto the motor. The operating points represented by Range 1.1, 1.2 . . . ,etc. are discrete points in the continuum of forward speed ratiosprovided by the EVT. For example in FIG. 2 b, a range of ratios from4.69 to 1.86 is achieved with the brake 154 engaged, and a range ofratios from 1.36 to 0.54 is achieved with the clutch 152 engaged.

The fifth operating mode includes the fixed “ratio” modes (F1, F2, F3and F4) corresponding with rows 13–16 of the operating mode table ofFIG. 2 b. In this mode the transmission operates like a conventionalautomatic transmission, with two torque transfer devices engaged tocreate a discrete transmission ratio. In fixed ratio F1 the clutch 150and brake 154 are engaged to achieve a fixed ratio of 2.78. In fixedratio F2, the brakes 154 and 155 are engaged to achieve a fixed ratio of1.78. In fixed ratio F3, the clutches 150 and 152 are engaged to achievea fixed ratio of 1.00. In fixed ratio F4, the clutch 152 is engaged andthe motor/generator 180 is braked by brake 155 to achieve a fixed ratioof 0.83.

As set forth above, the engagement schedule for the torque transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 2 b. FIG. 2 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 2 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 120 and the N_(R2)/N_(S2) value is the tooth ratio ofthe planetary gear set 130. Also, the chart of FIG. 2 b describes theratio steps that are attained utilizing the sample of tooth ratiosgiven. For example, the step ratio between first and second fixedforward torque ratios is 1.56, the step ratio between the second andthird fixed forward torque ratios is 1.78, and the step ratio betweenthe third and fourth fixed forward torque ratios is 1.20.

Description of a Third Exemplary Embodiment

With reference to FIG. 3 a, a powertrain 210 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral214. The transmission 214 is designed to receive at least a portion ofits driving power from the engine 12. As shown, the engine 12 has anoutput shaft that serves as the input member 17 of the transmission 214.A transient torque damper (not shown) may also be implemented betweenthe engine 12 and the input member 17 of the transmission 214.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member isoperatively connected to a planetary gear set in the transmission 214.An output member 19 of the transmission 214 is connected to a finaldrive 16.

The transmission 214 utilizes two differential gear sets, preferably inthe nature of planetary gear sets 220 and 230. The planetary gear set220 employs an outer gear member 224, typically designated as the ringgear. The ring gear 224 circumscribes an inner gear member 222,typically designated as the sun gear. A carrier 226 rotatably supports aplurality of planet gears 227 such that each planet gear 227 meshinglyengages both the outer, ring gear member 224 and the inner, sun gearmember 222 of the first planetary gear set 220.

The planetary gear set 230 also has an outer ring gear member 234 thatcircumscribes an inner sun gear member 232. A plurality of planet gears237 are also rotatably mounted in a carrier 236 such that each planetgear 237 simultaneously, and meshingly, engages both the outer ring gearmember 234 and the inner sun gear member 232 of the planetary gear set230.

The transmission input member 17 is connected with the ring gear 224,and the transmission output member 19 is connected to the carrier 226.An interconnecting member 270 continuously connects the carrier 226 ofthe planetary gear set 220 with the carrier 236 of the planetary gearset 230.

The transmission 214 also incorporates first and second motor/generators280 and 282, respectively. The stator of the first motor/generator 280is secured to the transmission housing 260. The rotor of the firstmotor/generator 280 is secured to the sun gear 222 of the planetary gearset 220.

The stator of the second motor/generator 282 is also secured to thetransmission housing 260. The rotor of the second motor/generator 282 issecured to the sun gear 232.

A first torque-transfer device, such as clutch 250, selectively connectsthe ring gear 224 of the planetary gear set 220 with the sun gear 232 ofthe planetary gear set 230. A second torque-transfer device, such asclutch 252, selectively connects the sun gear 222 of the planetary gearset 220 with the ring gear 234 of the planetary gear set 230. A thirdtorque-transfer device, such as a brake 254, selectively connects thering gear 234 of the planetary gear set 230 with the transmissionhousing 260. A fourth torque transfer device, such as the brake 255, isconnected in parallel with the motor/generator 282 for selectivelybraking rotation of the motor/generator 282. The first, second, thirdand fourth torque-transfer devices 250, 252, 254 and 255 are employed toassist in the selection of the operational modes of the hybridtransmission 214.

The hybrid transmission 214 receives power from the engine 12, and alsofrom electric power source 286, which is operably connected to acontroller 288.

The operating mode table of FIG. 3 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 214. These modes include the“battery reverse mode” (Batt Rev), “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “range 1.1, 1.2,1.3 . . . modes” and “fixed ratio modes” (F1, F2, F3, F4) as describedpreviously.

As set forth above the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 3 b. FIG. 3 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 3 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 220 and the N_(R2)/N_(S2) value is the tooth ratio ofthe planetary gear set 230. Also, the chart of FIG. 3 b describes theratio steps that are attained utilizing the sample of tooth ratiosgiven. For example, the step ratio between the first and second fixedforward torque ratios is 2.42, the step ratio between the second andthird fixed forward torque ratios 1.51, and the step ratio between thethird and fourth fixed forward torque ratios is 1.23. Each of the singlestep forward shifts between fixed ratios is a single transition shift.

Description of a Fourth Exemplary Embodiment

With reference to FIG. 4 a, a powertrain 310 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral314. The transmission 314 is designed to receive at least a portion ofits driving power from the engine 12.

As shown, the engine 12 has an output shaft that serves as the inputmember 17 of the transmission 314. A transient torque damper (not shown)may also be implemented between the engine 12 and the input member 17 ofthe transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connected to a planetary gear set in the transmission 314.An output member 19 of the transmission 314 is connected to a finaldrive 16.

The transmission 314 utilizes two planetary gear sets 320 and 330. Theplanetary gear set 320 employs an outer ring gear member 324 whichcircumscribes an inner sun gear member 322. A carrier 326 rotatablysupports a plurality of planet gears 327 such that each planet gear 327meshingly engages both the outer ring gear member 324 and the inner sungear member 322 of the first planetary gear set 320.

The planetary gear set 330 also has an outer ring gear member 334 thatcircumscribes an inner sun gear member 332. A plurality of planet gears337 are also rotatably mounted in a carrier 336 such that each planetgear member 337 simultaneously, and meshingly engages both the outer,ring gear member 334 and the inner, sun gear member 332 of the planetarygear set 330.

The transmission input member 17 is connected with the carrier 326 ofthe planetary gear set 320, and the transmission output member 19 isconnected with the carrier 336 of the planetary gear set 330. Aninterconnecting member 370 continuously connects the sun gear 322 of theplanetary gear set 320 with the sun gear 332 of the planetary gear set330.

The transmission 314 also incorporates first and second motor/generators380 and 382, respectively. The stator of the first motor/generator 380is secured to the transmission housing 360. The rotor of the firstmotor/generator 380 is secured to the ring gear 324 of the planetarygear set 320. The stator of the second motor/generator 382 is alsosecured to the transmission housing 360. The rotor of the secondmotor/generator 382 is secured to the sun gear 332 of the planetary gearset 330.

A first torque-transfer device, such as the clutch 350, selectivelyconnects the carrier 326 with the ring gear 324. A secondtorque-transfer device, such as the clutch 352, selectively connects thecarrier 336 with the ring gear 324. A third torque-transfer device, suchas brake 354, selectively connects the ring gear 334 with thetransmission housing 360. A fourth torque transfer device, such as thebrake 355, is connected in parallel with the motor/generator 380 forselectively braking rotation of the motor/generator 380. The first,second, third and fourth torque-transfer devices 350, 352, 354 and 355are employed to assist in the selection of the operational modes of thetransmission 314.

The hybrid transmission 314 receives power from the engine 12, and alsoexchanges power with an electric power source 386, which is operablyconnected to a controller 388.

The operating mode table of FIG. 4 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 314. These modes include the“battery reverse mode” (Batt Rev), the “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “continuouslyvariable transmission range modes” (Range 1.1, 1.2, 1.3 . . . ) and“fixed ratio modes” (F1, F2, F3, F4) as described previously.

As set forth above, the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 4 b. FIG. 4 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 4 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 320 and the N_(R2)/N_(S2) value is the tooth ratio ofthe planetary gear set 330. Also, the chart of FIG. 4 b describes theratio steps that are attained utilizing the sample of tooth ratiosgiven. For example, the step ratio between first and second fixedforward torque ratios is 1.82, the step ratio between the second andthird fixed forward torque ratios is 2.20, and the step ratio betweenthe third and fourth fixed forward torque ratios is 1.67. Each of thesingle step forward shifts between fixed ratios is a single transitionshift.

Description of a Fifth Exemplary Embodiment

With reference to FIG. 5 a, a powertrain 410 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral414. The transmission 414 is designed to receive at least a portion ofits driving power from the engine 12.

As shown, the engine 12 has an output shaft that serves as the inputmember 17 of the transmission 414. A transient torque damper (not shown)may also be implemented between the engine 12 and the input member 17 ofthe transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connected to a planetary gear set in the transmission 414.An output member 19 of the transmission 414 is connected to a finaldrive 16.

The transmission 414 utilizes two planetary gear sets 420 and 430. Theplanetary gear set 420 employs an outer ring gear member 424 whichcircumscribes an inner sun gear member 422. A carrier 426 rotatablysupports a plurality of planet gears 427 such that each planet gear 427meshingly engages both the outer ring gear member 424 and the inner sungear member 422 of the first planetary gear set 420.

The planetary gear set 430 also has an outer ring gear member 434 thatcircumscribes an inner sun gear member 432. A plurality of planet gears437 are also rotatably mounted in a carrier 436 such that each planetgear member 437 simultaneously, and meshingly engages both the outer,ring gear member 434 and the inner, sun gear member 432 of the planetarygear set 430.

The transmission input member 17 is continuously connected with thecarrier 426, and the transmission output member 19 is continuouslyconnected with the carrier 436. An interconnecting member 470continuously connects the sun gear 422 with the sun gear 432.

The transmission 414 also incorporates first and second motor/generators480 and 482, respectively. The stator of the first motor/generator 480is secured to the transmission housing 460. The rotor of the firstmotor/generator 480 is secured to the ring gear 424.

The stator of the second motor/generator 482 is also secured to thetransmission housing 460. The rotor of the second motor/generator 482 issecured to the sun gear 432.

A first torque-transfer device, such as a clutch 450, selectivelyconnects the ring gear 424 with the carrier 426. A secondtorque-transfer device, such as clutch 452, selectively connects thering gear 424 with the ring gear 434. A third torque-transfer device,such as brake 454, selectively connects the ring gear 434 with thetransmission housing 460. A fourth torque transfer device, such as thebrake 455, is connected in parallel with the motor/generator 480 forselectively braking rotation of the motor/generator 480. The first,second, third and fourth torque-transfer devices 450, 452, 454 and 455are employed to assist in the selection of the operational modes of thetransmission 414. The hybrid transmission 414 receives power from theengine 12 and also from an electric power source 486, which is operablyconnected to a controller 488.

The operating mode table of FIG. 5 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 414. These modes include the“battery reverse mode” (Batt Rev), the “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “continuouslyvariable transmission range modes” (Range 1.1, 1.2, 1.3 . . . ) and“fixed ratio modes” (F1, F2, F3, F4) as described previously.

The transmission 414 is a single mode transmission providing ratiosbetween 4.69 and 0.54.

As set forth above, the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 5 b. FIG. 5 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 5 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 420 and the N_(R2)/N_(S2) value is the tooth ratio ofthe planetary gear set 430. Also, the chart of FIG. 5 b describes theratio steps that are attained utilizing the sample of tooth ratiosgiven. For example, the step ratio between first and second fixedforward torque ratios is 3.01, the step ratio between the second andthird fixed forward torque ratios is 1.33, and the step ratio betweenthe third and fourth fixed forward torque ratios is 1.49. Each of thesingle step forward shifts between fixed ratios is a single transitionshift.

Description of a Sixth Exemplary Embodiment

With reference to FIG. 6 a, a powertrain 510 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral514. The transmission 514 is designed to receive at least a portion ofits driving power from the engine 12.

As shown, the engine 12 has an output shaft that serves as the inputmember 17 of the transmission 514. A transient torque damper (not shown)may also be implemented between the engine 12 and the input member 17 ofthe transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connected to a planetary gear set in the transmission 514.An output member 19 of the transmission 514 is connected to a finaldrive 16.

The transmission 514 utilizes two planetary gear sets 520 and 530. Theplanetary gear set 520 employs an outer ring gear member 524 whichcircumscribes an inner sun gear member 522. A carrier 526 rotatablysupports a plurality of planet gears 527 such that each planet gear 527meshingly engages both the outer ring gear member 524 and the inner sungear member 522 of the first planetary gear set 520.

The planetary gear set 530 also has an outer ring gear member 534 thatcircumscribes an inner sun gear member 532. A plurality of planet gears537 are also rotatably mounted in a carrier 536 such that each planetgear member 537 simultaneously, and meshingly engages both the outer,ring gear member 534 and the inner, sun gear member 532 of the planetarygear set 530.

The transmission input member 17 is continuously connected with thecarrier 526, and the transmission output member 19 is continuouslyconnected with the carrier 536. An interconnecting member 570continuously connects the sun gear with the sun gear 532.

The transmission 514 also incorporates first and second motor/generators580 and 582, respectively. The stator of the first motor/generator 580is secured to the transmission housing 560. The rotor of the firstmotor/generator 580 is secured to the sun gear 522.

The stator of the second motor/generator 582 is also secured to thetransmission housing 560. The rotor of the second motor/generator 582 issecured to the ring gear 524.

A first torque-transfer device, such as a clutch 550, selectivelyconnects the ring gear 524 with the carrier 526. A secondtorque-transfer device, such as a clutch 552, selectively connects thecarrier 526 with the ring gear 534. A third torque-transfer device, suchas a brake 554, selectively connects the ring gear 534 with thetransmission housing 560. A fourth torque transfer device, such as thebrake 555, is connected in parallel with the motor/generator 580 forselectively braking rotation of the motor/generator 580. The first,second, third and fourth torque-transfer devices 550, 552, 554 and 555are employed to assist in the selection of the operational modes of thehybrid transmission 514.

The hybrid transmission 514 receives power from the engine 12, and alsoexchanges power with an electric power source 586, which is operablyconnected to a controller 588.

The operating mode table of FIG. 6 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 514. These modes include the“battery reverse mode” (Batt Rev), the “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “continuouslyvariable transmission range modes” (Range 1.1, 1.2, 1.3 . . . ) and“fixed ratio modes” (F1, F2, F3, F4) as described previously.

As set forth above, the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 6 b. FIG. 6 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 6 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 520 and the N_(R2)/N_(S2) value is the tooth ratio ofthe planetary gear set 530. Also, the chart of FIG. 4 b describes theratio steps that are attained utilizing the sample of tooth ratiosgiven. For example, the step ratio between first and second fixedforward torque ratios is 1.43; the step ratio between the second andthird fixed forward torque ratios is 1.94, and the step ratio betweenthe third and fourth fixed forward torque ratios is 1.43.

Description of a Seventh Exemplary Embodiment

With reference to FIG. 7 a, a powertrain 610 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral614. The transmission 614 is designed to receive at least a portion ofits driving power from the engine 12.

As shown, the engine 12 has an output shaft that serves as the inputmember 17 of the transmission 614. A transient torque damper (not shown)may also be implemented between the engine 12 and the input member 17 ofthe transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connected to a planetary gear set in the transmission 614.An output member 19 of the transmission 614 is connected to a finaldrive 16.

The transmission 614 utilizes two planetary gear sets 620 and 630. Theplanetary gear set 620 employs an outer ring gear member 624 whichcircumscribes an inner sun gear member 622. A carrier 626 rotatablysupports a plurality of planet gears 627 such that each planet gear 627meshingly engages both the outer ring gear member 624 and the inner sungear member 622 of the first planetary gear set 620.

The planetary gear set 630 also has an outer ring gear member 634 thatcircumscribes an inner sun gear member 632. A plurality of planet gears637 are also rotatably mounted in a carrier 636 such that each planetgear member 637 simultaneously, and meshingly engages both the outer,ring gear member 634 and the inner, sun gear member 632 of the planetarygear set 630.

The transmission input member 17 is continuously connected with the ringgear 624, and the transmission output member 19 is continuouslyconnected with the carrier 636. An interconnecting member 670continuously connects the sun gear 622 with the ring gear 634.

The transmission 614 also incorporates first and second motor/generators680 and 682, respectively. The stator of the first motor/generator 680is secured to the transmission housing 660. The rotor of the firstmotor/generator 680 is secured to the sun gear 632.

The stator of the second motor/generator 682 is also secured with thetransmission housing 660. The rotor of the second motor/generator 682 issecured to the carrier 626.

A first torque-transfer device, such as a clutch 650, selectivelyconnects the ring gear 624 with the sun gear 632. A secondtorque-transfer device, such as a clutch 652, selectively connects thecarrier 626 with the carrier 636. A third torque-transfer device, suchas a brake 654, selectively connects the ring gear 634 with thetransmission housing 660. A fourth torque transfer device, such as thebrake 655, is connected in parallel with the motor/generator 680 forselectively braking rotation of the motor/generator 680. The first,second, third and fourth torque-transfer devices 650, 652, 654 and 655are employed to assist in the selection of the operational modes of thehybrid transmission 614.

The hybrid transmission 614 receives power from the engine 12, and alsoexchanges power with an electric power source 686, which is operablyconnected to a controller 688.

The operating mode table of FIG. 7 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 614. These modes include the“battery reverse mode” (Batt Rev), the “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “continuouslyvariable transmission range modes” (Range 1.1, 1.2, 1.3 . . . ) and“fixed ratio modes” (F1, F2, F3, F4) as described previously.

As set forth above, the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 7 b. FIG. 7 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 7 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 620 and the N_(R2)/N_(S2) value is the tooth ratio ofthe planetary gear set 630. Also, the chart of FIG. 7 b describes theratio steps that are attained utilizing the sample of tooth ratiosgiven. For example, the step ratio between first and second fixedforward torque ratios is 3.31, the step ratio between the second andthird fixed forward torque ratios is 1.21, and the step ratio betweenthe third and fourth fixed forward torque ratios is 1.43. Each of thesingle step forward shifts between fixed ratios is a single transitionshift.

Description of an Eighth Exemplary Embodiment

With reference to FIG. 8 a, a powertrain 710 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral714. The transmission 714 is designed to receive at least a portion ofits driving power from the engine 12.

As shown, the engine 12 has an output shaft that serves as the inputmember 17 of the transmission 714. A transient torque damper (not shown)may also be appointed between the engine 12 and the input member 17 ofthe transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connected to a planetary gear set in the transmission 714.An output member 19 of the transmission 714 is connected to a finaldrive 16.

The transmission 714 utilizes two planetary gear sets 720 and 730. Theplanetary gear set 720 employs an outer ring gear member 724 whichcircumscribes an inner sun gear member 722. A carrier 726 rotatablysupports a plurality of planet gears 727 such that each planet gear 727meshingly engages both the outer ring gear member 724 and the inner sungear member 722 of the first planetary gear set 720.

The planetary gear set 730 also has an outer ring gear member 734 thatcircumscribes an inner sun gear member 732. A plurality of planet gears737 are also rotatably mounted in a carrier 736 such that each planetgear member 737 simultaneously, and meshingly engages both the outer,ring gear member 734 and the inner, sun gear member 732 of the planetarygear set 730.

The transmission input member 17 is continuously connected with thecarrier 726, and the transmission output member 19 is continuouslyconnected with the ring gear 724. An interconnecting member 770continuously connects the ring gear 724 with the carrier 736.

The transmission 714 also incorporates first and second motor/generators780 and 782, respectively. The stator of the first motor/generator 780is secured to the transmission housing 760. The rotor of the firstmotor/generator 780 is secured to the sun gear 722.

The stator of the second motor/generator 782 is also secured to thetransmission housing 760. The rotor of the second motor/generator 782 issecured to the sun gear 732.

A first torque-transfer device, such as a clutch 750, selectivelyconnects the sun gear 722 with the sun gear 732. A secondtorque-transfer device, such as a clutch 752, selectively connects thecarrier 726 with the sun gear 732. A third torque-transfer device, suchas the brake 754, selectively connects the ring gear 734 with thetransmission housing 760. A fourth torque transfer device, such as thebrake 755, is connected in parallel with the motor/generator 780 forselectively braking rotation of the motor/generator 780. The first,second, third and fourth torque-transfer devices 750, 752, 754 and 755are employed to assist in the selection of the operational modes of thehybrid transmission 714.

The hybrid transmission 714 receives power from the engine 12, and alsoexchanges power with an electric power source 786, which is operablyconnected to a controller 788.

The operating mode table of FIG. 8 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 714. These modes include the“battery reverse mode” (Batt Rev), the “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “continuouslyvariable transmission range modes” (Range 1.1, 1.2, 1.3 . . . ) and“fixed ratio modes” (F1, F2, F3, F4) as described previously.

As set forth above, the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 8 b. FIG. 8 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 8 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 720 and the N_(R2)/N_(S2) value is the tooth ratio ofthe planetary gear set 730. Also, the chart of FIG. 8 b describes theratio steps that are attained utilizing the sample of tooth ratiosgiven. For example, the step ratio between first and second fixedforward torque ratios is 2.27, the step ratio between the second andthird fixed forward torque ratios is 1.76, and the step ratio betweenthe third and fourth fixed forward torque ratios is 1.33.

Description of a Ninth Exemplary Embodiment

With reference to FIG. 9 a, a powertrain 810 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral814. The transmission 814 is designed to receive at least a portion ofits driving power from the engine 12.

As shown, the engine 12 has an output shaft that serves as the inputmember 17 of the transmission 814. A transient torque damper (not shown)may also be implemented between the engine 12 and the input member 17 ofthe transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connected to a planetary gear set in the transmission 814.An output member 19 of the transmission 814 is connected to a finaldrive 16.

The transmission 814 utilizes two planetary gear sets 820 and 830. Theplanetary gear set 820 employs an outer ring gear member 824 whichcircumscribes an inner sun gear member 822. A carrier 826 rotatablysupports a plurality of planet gears 827 such that each planet gear 827meshingly engages both the outer ring gear member 824 and the inner sungear member 822 of the first planetary gear set 820.

The planetary gear set 830 also has an outer ring gear member 834 thatcircumscribes an inner sun gear member 832. A plurality of planet gears837 are also rotatably mounted in a carrier 836 such that each planetgear member 837 simultaneously, and meshingly engages both the outer,ring gear member 834 and the inner, sun gear member 832 of the planetarygear set 830.

The transmission input member 17 is continuously connected with thecarrier 826, and the transmission output member 19 is continuouslyconnected with the ring gear 824. An interconnecting member 870continuously connects the ring gear 824 with the carrier 836.

The transmission 814 also incorporates first and second motor/generators880 and 882, respectively. The stator of the first motor/generator 880is secured to the transmission housing 860. The rotor of the firstmotor/generator 880 is secured to the ring gear 834.

The stator of the second motor/generator 882 is also secured to thetransmission housing 860. The rotor of the second motor/generator 882 issecured to the sun gear 832.

A first torque-transfer device, such as a clutch 850, selectivelyconnects the sun gear 822 with the sun gear 832. A secondtorque-transfer device, such as clutch 852, selectively connects thecarrier 826 with the sun gear 832. A third torque-transfer device, suchas brake 854, selectively connects the sun gear 822 with thetransmission housing 860. A fourth torque transfer device, such as thebrake 855, is connected in parallel with the motor/generator 880 forselectively braking rotation of the motor/generator 880. A fifth torquetransfer device, such as the brake 857, is connected in parallel withthe motor/generator 882 for selectively braking rotation of themotor/generator 882. The first, second, third, fourth and fifthtorque-transfer devices 850, 852, 854, 855 and 857 are employed toassist in the selection of the operational modes of the hybridtransmission 814.

The hybrid transmission 814 receives power from the engine 12, andexchanges power with an electric power source 886, which is operablyconnected to a controller 888.

The operating mode table of FIG. 9 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 814. These modes include the“battery reverse mode” (Batt Rev), the “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “continuouslyvariable transmission range modes” (Range 1.1, 1.2, 1.3 . . . ) and“fixed ratio modes” (F1, F2, F3, F4) as described previously.

As set forth above, the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 9 b. FIG. 9 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 9 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 820 and the N_(R2)/N_(S2) value is the tooth ratio ofthe planetary gear set 830. Also, the chart of FIG. 9 b describes theratio steps that are attained utilizing the sample of tooth ratiosgiven. For example, the step ratio between first and second fixedforward torque ratios is 2.27, the step ratio between the second andthird fixed forward torque ratios is 1.76, and the step ratio betweenthe third and fourth fixed forward torque ratios is 1.33. Each of thesingle step forward shifts between fixed ratios is a single transitionshift.

Description of a Tenth Exemplary Embodiment

With reference to FIG. 10 a, a powertrain 910 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral914. The transmission 914 is designed to receive at least a portion ofits driving power from the engine 12.

As shown, the engine 12 has an output shaft that serves as the inputmember 17 of the transmission 914. A transient torque damper (not shown)may also be implemented between the engine 12 and the input member 17 ofthe transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connected to a planetary gear set in the transmission 914.An output member 19 of the transmission 914 is connected to a finaldrive 16.

The transmission 914 utilizes two planetary gear sets 920 and 930. Theplanetary gear set 920 employs an outer ring gear member 924 whichcircumscribes an inner sun gear member 922. A carrier 926 rotatablysupports a plurality of planet gears 927 such that each planet gear 927meshingly engages both the outer ring gear member 924 and the inner sungear member 922 of the first planetary gear set 920.

The planetary gear set 930 also has an outer ring gear member 934 thatcircumscribes an inner sun gear member 932. A plurality of planet gears937 are also rotatably mounted in a carrier 936 such that each planetgear member 937 simultaneously, and meshingly engages both the outer,ring gear member 934 and the inner, sun gear member 932 of the planetarygear set 930.

The transmission input member 17 is continuously connected with thecarrier 926. The transmission output member 19 is continuously connectedwith the carrier 936. An interconnecting member 970 continuouslyconnects the sun gear 922 with the sun gear 932.

A first torque-transfer device, such as a clutch 950, selectivelyconnects the sun gear 922 with the carrier 926. A second torque-transferdevice, such as a clutch 952, selectively connects the ring gear 924with the carrier 936. A third torque-transfer device, such as brake 954,selectively connects the carrier 936 with the transmission housing 960.A fourth torque transfer device, such as the brake 955, is connected inparallel with the motor/generator 980 for selectively braking rotationof the motor/generator 980. A fifth torque transfer device, such as thebrake 957, is connected in parallel with the motor/generator 982 forselectively braking rotation of the motor/generator 982. The first,second, third, fourth and fifth torque-transfer devices 950, 952, 954,955 and 957 are employed to assist in the selection of the operationalmodes of the hybrid transmission 914.

The hybrid transmission 914 receives power from the engine 12, and alsoexchanges power with an electric power source 986, which is operablyconnected to a controller 988.

The operating mode table of FIG. 10 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 914. These modes include the“battery reverse mode” (Batt Rev), the “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “continuouslyvariable transmission range modes” (Range 1.1, 1.2, 1.3 . . . ) and“fixed ratio modes” (F1, F2, F3, F4) as described previously.

As set forth above, the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 10 b. FIG. 10 b also provides an example of torque ratios thatare available utilizing the ring gear/sun gear tooth ratios given by wayof example in FIG. 10 b. The N_(R1)/N_(S1) value is the tooth ratio ofthe planetary gear set 920 and the N_(R2)/N_(S2) value is the toothratio of the planetary gear set 930. Also, the chart of FIG. 10 bdescribes the ratio steps that are attained utilizing the sample oftooth ratios given. For example, the step ratio between first and secondfixed forward torque ratios is 2.11, the step ratio between the secondand third fixed forward torque ratios is 1.90, and the step ratiobetween the third and fourth fixed forward torque ratios is 1.43. Eachof the single step forward shifts between fixed ratios is a singletransition shift.

Description of an Eleventh Exemplary Embodiment

With reference to FIG. 11 a, a powertrain 1010 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral1014. The transmission 1014 is designed to receive at least a portion ofits driving power from the engine 12.

As shown, the engine 12 has an output shaft that serves as the inputmember 17 of the transmission 1014. A transient torque damper (notshown) may also be implemented between the engine 12 and the inputmember 17 of the transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connected to a planetary gear set in the transmission 1014.An output member 19 of the transmission 1014 is connected to a finaldrive 16.

The transmission 1014 utilizes two planetary gear sets 1020 and 1030.The planetary gear set 1020 employs an outer ring gear member 1024 whichcircumscribes an inner sun gear member 1022. A carrier 1026 rotatablysupports a plurality of planet gears 1027 such that each planet gear1027 meshingly engages both the outer ring gear member 1024 and theinner sun gear member 1022 of the first planetary gear set 1020.

The planetary gear set 1030 also has an outer ring gear member 1034 thatcircumscribes an inner sun gear member 1032. A plurality of planet gears1037 are also rotatably mounted in a carrier 1036 such that each planetgear member 1037 simultaneously, and meshingly engages both the outer,ring gear member 1034 and the inner, sun gear member 1032 of theplanetary gear set 1030.

The transmission input member 17 is continuously connected with thecarrier 1026, and the transmission output member 19 is continuouslyconnected with the ring gear 1024. An interconnecting member 1070continuously connects the ring gear 1024 with the carrier 1036.

The transmission 1014 also incorporates first and secondmotor/generators 1080 and 1082, respectively. The stator of the firstmotor/generator 1080 is secured to the transmission housing 1060. Therotor of the first motor/generator 1080 is secured to the sun gear 1032.

The stator of the second motor/generator 1082 is also secured to thetransmission housing 1060. The rotor of the second motor/generator 1082is secured to the ring gear 1034.

A first torque-transfer device, such as a clutch 1050, selectivelyconnects the carrier 1026 with the ring gear 1034. A secondtorque-transfer device, such as a clutch 1052, selectively connects thesun gear 1022 with the sun gear 1032. A third torque-transfer device,such as brake 1054, selectively connects the carrier 1036 with thetransmission housing 1060. A fourth torque transfer device, such as thebrake 1055, is connected in parallel with the motor/generator 1080 forselectively braking rotation of the motor/generator 1080. A fifth torquetransfer device, such as the brake 1057, is connected in parallel withthe motor/generator 1082 for selectively braking rotation of themotor/generator 1082. The first, second, third, fourth and fifthtorque-transfer devices 1050, 1052, 1054, 1055 and 1057 are employed toassist in the selection of the operational modes of the hybridtransmission 1014.

The hybrid transmission 1014 receives power from the engine 12, and alsoexchanges power with the electric power source 1086, which is operablyconnected to a controller 1088.

The operating mode table of FIG. 11 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 1014. These modes include the“battery reverse mode” (Batt Rev), the “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “continuouslyvariable transmission range modes” (Range 1.1, 1.2, 1.3 . . . ) and“fixed ratio modes” (F1, F2, F3, F4) as described previously.

As set forth above, the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 11 b. FIG. 11 b also provides an example of torque ratios thatare available utilizing the ring gear/sun gear tooth ratios given by wayof example in FIG. 11 b. The N_(R1)/N_(S1) value is the tooth ratio ofthe planetary gear set 1020 and the N_(R2)/N_(S2) value is the toothratio of the planetary gear set 1030. Also, the chart of FIG. 11 bdescribes the ratio steps that are attained utilizing the sample oftooth ratios given. For example, the step ratio between first and secondfixed forward torque ratios is 2.27, the step ratio between the secondand third fixed forward torque ratios is 1.76, and the step ratiobetween the third and fourth fixed forward torque ratios is 1.33. Eachof the single step forward shifts between fixed ratios is a singletransition shift.

Description of a Twelfth Exemplary Embodiment

With reference to FIG. 12 a, a powertrain 1110 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral1114. The transmission 1114 is designed to receive at least a portion ofits driving power from the engine 12.

As shown, the engine 12 has an output shaft that serves as the inputmember 17 of the transmission 1114. A transient torque damper (notshown) may also be implemented between the engine 12 and the inputmember 17 of the transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connected to a planetary gear set in the transmission 1114.An output member 19 of the transmission 1114 is connected to a finaldrive 16.

The transmission 1114 utilizes two planetary gear sets 1120 and 1130.The planetary gear set 1120 employs an outer ring gear member 1124 whichcircumscribes an inner sun gear member 1122. A carrier 1126 rotatablysupports a plurality of planet gears 1127 such that each planet gear1127 meshingly engages both the outer ring gear member 1124 and theinner sun gear member 1122 of the first planetary gear set 1120.

The planetary gear set 1130 also has an outer ring gear member 1134 thatcircumscribes an inner sun gear member 1132. A plurality of planet gears1137 are also rotatably mounted in a carrier 1136 such that each planetgear member 1137 simultaneously, and meshingly engages both the outer,ring gear member 1134 and the inner, sun gear member 1132 of theplanetary gear set 1130.

The transmission input member 17 is continuously connected with the sungear 1122, and the transmission output member 19 is continuouslyconnected with the carrier 1136. The interconnecting member 1170continuously connects the ring gear 1124 with the ring gear 1134.

The transmission 1114 also incorporates first and secondmotor/generators 1180 and 1182, respectively. The stator of the firstmotor/generator 1180 is secured to the transmission housing 1160. Therotor of the first motor/generator 1180 is secured to the carrier 1126.

The stator of the second motor/generator 1182 is also secured to thetransmission housing 1160. The rotor of the second motor/generator 1182is secured to the sun gear 1132.

A first torque-transfer device, such as a clutch 1150, selectivelyconnects the ring gear 1124 with the carrier 1126. A secondtorque-transfer device, such as clutch 1152, selectively connects thecarrier 1126 with the carrier 1136. A third torque-transfer device, suchas the brake 1154, selectively connects the ring gear 1124 with thetransmission housing 1160. A fourth torque transfer device, such as thebrake 1155, is connected in parallel with the motor/generator 1182 forselectively braking rotation of the motor/generator 1182. The first,second, third and fourth torque-transfer devices 1150, 1152, 1154 and1155 are employed to assist in the selection of the operational modes ofthe transmission 1114.

The hybrid transmission 1114 receives power from the engine 12, and alsoexchanges power with the electric power source 1186, which is operablyconnected to a controller 1188.

The operating mode table of FIG. 12 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 1114. These modes include the“battery reverse mode” (Batt Rev), the “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “continuouslyvariable transmission range modes” (Range 1.1, 1.2, 1.3 . . . and “fixedratio modes” (F1, F2, F3, F4) as described previously.

As set forth above, the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 12 b. FIG. 12 b also provides an example of torque ratios thatare available utilizing the ring gear/sun gear tooth ratios given by wayof example in FIG. 12 b. The N_(R1)/N_(S1) value is the tooth ratio ofthe planetary gear set 1120 and the N_(R2)/N_(S2) value is the toothratio of the planetary gear set 1030. Also, the chart of FIG. 12 bdescribes the ratio steps that are attained utilizing the sample oftooth ratios given. For example, the step ratio between first and secondfixed forward torque ratios is 1.43, the step ratio between the secondand third fixed forward torque ratios is 1.94, and the step ratiobetween the third and fourth fixed forward torque ratios is 1.43.

Description of a Thirteenth Exemplary Embodiment

With reference to FIG. 13 a, a powertrain 1210 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral1214. The transmission 1214 is designed to receive at least a portion ofits driving power from the engine 12.

As shown, the engine 12 has an output shaft that serves as the inputmember 17 of the transmission 1214. A transient torque damper (notshown) may also be implemented between the engine 12 and the inputmember 17 of the transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connected to a planetary gear set in the transmission 1214.An output member 19 of the transmission 1214 is connected to a finaldrive 16.

The transmission 1214 utilizes two planetary gear sets 1220 and 1230.The planetary gear set 1220 employs an outer ring gear member 1224 whichcircumscribes an inner sun gear member 1222. A carrier 1226 rotatablysupports a plurality of planet gears 1227 such that each planet gear1227 meshingly engages both the outer ring gear member 1224 and theinner sun gear member 1222 of the first planetary gear set 1220.

The planetary gear set 1230 also has an outer ring gear member 1234 thatcircumscribes an inner sun gear member 1232. A plurality of planet gears1237 are also rotatably mounted in a carrier 1236 such that each planetgear member 1237 simultaneously, and meshingly engages both the outer,ring gear member 1234 and the inner, sun gear member 1232 of theplanetary gear set 1230.

The transmission input member 17 is continuously connected with the sungear 1222, and the transmission output member 19 is continuouslyconnected with the ring gear 1234. An interconnecting member 1270continuously connects the ring gear 1224 with the sun gear 1232.

The transmission 1214 also incorporates first and secondmotor/generators 1280 and 1282, respectively. The stator of the firstmotor/generator 1280 is secured to the transmission housing 1260. Therotor of the first motor/generator 1280 is secured to the carrier 1226.The stator of the second motor/generator 1282 is also secured to thetransmission housing 1260. The rotor of the second motor/generator 1282is secured to the ring gear 1224.

A first torque-transfer device, such as a clutch 1250, selectivelyconnects the sun gear 1222 with the carrier 1236. A secondtorque-transfer device, such as clutch 1252, selectively connects thecarrier 1226 with the carrier 1236. A third torque-transfer device, suchbrake 1254, selectively connects the carrier 1236 with the transmissionhousing 1260. A fourth torque transfer device, such as the brake 1255,is connected in parallel with the motor/generator 1280 for selectivelybraking rotation of the motor/generator 1280. A fifth torque transferdevice, such as the brake 1257, is connected in parallel with themotor/generator 1282 for selectively braking rotation of themotor/generator 1282. The first, second, third, fourth and fifthtorque-transfer devices 1250, 1252, 1254, 1255 and 1257 are employed toassist in the selection of the operational modes of the hybridtransmission 1214.

The hybrid transmission 1214 receives power from the engine 12, and alsoexchanges power with an electric power source 1286, which is operablyconnected to a controller 1288.

The operating mode table of FIG. 13 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 1214. These modes include the“battery reverse mode” (Batt Rev), the “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “continuouslyvariable transmission range modes” (Range 1.1, 1.2, 1.3 . . . ) and“fixed ratio modes” (F1, F2, F3, F4) as described previously.

As set forth above, the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 13 b. FIG. 13 b also provides an example of torque ratios thatare available utilizing the ring gear/sun gear tooth ratios given by wayof example in FIG. 13 b. The N_(R1)/N_(S1) value is the tooth ratio ofthe planetary gear set 1220 and the N_(R2)/N_(S2) value is the toothratio of the planetary gear set 1230. Also, the chart of FIG. 13 bdescribes the ratio steps that are attained utilizing the sample oftooth ratios given. For example, the step ratio between first and secondfixed forward torque ratios is 1.73, the step ratio between the secondand third fixed forward torque ratios is 1.68, and the step ratiobetween the third and fourth fixed forward torque ratios is 1.56. Eachof the single step forward shifts between fixed ratios is a singletransition shift.

Description of a Fourteenth Exemplary Embodiment

With reference to FIG. 14 a, a powertrain 1310 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral1314. The transmission 1314 is designed to receive at least a portion ofits driving power from the engine 12.

As shown, the engine 12 has an output shaft that serves as the inputmember 17 of the transmission 1314. A transient torque damper (notshown) may also be implemented between the engine 12 and the inputmember 17 of the transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connected to a planetary gear set in the transmission 1314.An output member 19 of the transmission 1314 is connected to a finaldrive 16.

The transmission 1314 utilizes two planetary gear sets 1320 and 1330.The planetary gear set 1320 employs an outer ring gear member 1324 whichcircumscribes an inner sun gear member 1322. A carrier 1326 rotatablysupports a plurality of planet gears 1327 such that each planet gear1327 meshingly engages both the outer ring gear member 1324 and theinner sun gear member 1322 of the first planetary gear set 1320.

The planetary gear set 1330 also has an outer ring gear member 1334 thatcircumscribes an inner sun gear member 1332. A plurality of planet gears1337, 1338 are also rotatably mounted in a carrier 1336 such that eachplanet gear member 1337 meshingly engages the inner, sun gear member1332 of the planetary gear set 1330, and each planet gear member 1338meshingly engages the outer, ring gear member 1334.

The transmission input member 17 is continuously connected with the ringgear 1324, and the transmission output member 19 is continuouslyconnected with the carrier 1346. An interconnecting member 1370continuously connects the ring gear 1324 with the sun gear 1332.

The transmission 1314 also incorporates first and secondmotor/generators 1380 and 1382, respectively. The stator of the firstmotor/generator 1380 is secured to the transmission housing 1360. Therotor of the first motor/generator 1380 is secured to the sun gear 1322.

The stator of the second motor/generator 1382 is also secured to thetransmission housing 1360. The rotor of the second motor/generator 1382is secured to the ring gear 1324.

A first torque-transfer device, such as a clutch 1350, selectivelyconnects the carrier 1326 with the ring gear 1324. A secondtorque-transfer device such as clutch 1352 selectively connects the ringgear 1334 with the sun gear 1332. A third torque-transfer device, suchas brake 1354, selectively connects the carrier 1336 with thetransmission housing 1360. A fourth torque transfer device, such as thebrake 1355, is connected in parallel with the motor/generator 1380 forselectively braking rotation of the motor/generator 1380. The first,second, third and fourth torque-transfer devices 1350, 1352, 1354 and1355 are employed to assist in the selection of the operational modes ofthe transmission 1314.

The hybrid transmission 1314 receives power from the engine 12, and alsoexchanges power with an electric power source 1386, which is operativelyconnected to a controller 1388.

The operating mode table of FIG. 14 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 1314. These modes include the“battery reverse mode” (Batt Rev), the “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “continuouslyvariable transmission range modes” (Range 1.1, 1.2, 1.3 . . . ) and“fixed ratio modes” (F1, F2, F3, F4) as described previously.

As set forth above, the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 14 b. FIG. 14 b also provides an example of torque ratios thatare available utilizing the ring gear/sun gear tooth ratios given by wayof example in FIG. 14 b. The N_(R1)/N_(S1) value is the tooth ratio ofthe planetary gear set 1320 and the N_(R2)/N_(S2) value is the toothratio of the planetary gear set 1330. Also, the chart of FIG. 14 bdescribes the ratio steps that are attained utilizing the sample oftooth ratios given. For example, the ratio step between first and secondfixed forward torque ratios is 1.43, the ratio step between the secondand third fixed forward torque ratios is 1.94, and the ratio stepbetween the third and fourth fixed forward torque ratios is 1.43.

In the claims, the language “continuously connected” or “continuouslyconnecting” refers to a direct connection or a proportionally gearedconnection, such as gearing to an offset axis.

While various preferred embodiments of the present invention aredisclosed, it is to be understood that the concepts of the presentinvention are susceptible to numerous changes apparent to one skilled inthe art. Therefore, the scope of the present invention is not to belimited to the details shown and described but is intended to includeall variations and modifications which come within the scope of theappended claims.

1. An electrically variable transmission comprising: an input member toreceive power from an engine; an output member; first and secondmotor/generators; not more than first and second differential gear setseach having first, second and third members, wherein said first, second,and third members comprise a ring gear, sun gear, and carrier, in anyorder; and wherein each of said first and second differential gear setsincludes not more than one ring gear, not more than one carrier, and notmore than one sun gear; said input member being continuously connectedwith at least one member of said gear sets, and said output member beingcontinuously connected with another member of said gear sets; aninterconnecting member continuously connecting said first member of saidfirst gear set with said first member of said second gear set; saidfirst motor/generator being continuously connected with a member of saidfirst or second gear set; said second motor/generator being continuouslyconnected with a member of said first or second gear set which isdifferent from said member connected with said first motor/generator; afirst torque transfer device selectively connecting a member of saidfirst gear set with another member of said first or second gear set; asecond torque transfer device selectively connecting a member of saidsecond gear set with another member of said first or second gear set,the pair of members connected by said second torque transfer devicebeing different from the pair of members connected by said first torquetransfer device; a third torque transfer device selectively grounding amember of said first or second gear set; and a fourth torque transferdevice connected in parallel with said first or second motor/generatorfor braking rotation thereof; wherein said first, second, third andfourth torque transfer devices are engageable alone to provide anelectrically variable transmission with a continuously variable range ofspeed ratios and in pairs to provide four fixed forward speed ratios. 2.The electrically variable transmission of claim 1, wherein said first,second, third and fourth torque transfer devices and said first andsecond motor/generators are operable to provide five operating modes inthe electrically variable transmission, including battery reverse mode,EVT reverse mode, reverse and forward launch modes, continuouslyvariable transmission range mode, and fixed ratio mode.
 3. Theelectrically variable transmission of claim 1, wherein said first andsecond differential gear sets are planetary gear sets.
 4. Theelectrically variable transmission of claim 3, wherein at least onecarrier of said planetary gear sets is a double-pinion carrier.
 5. Theelectrically variable transmission of claim 3, wherein carriers of eachof said planetary gear sets are single-pinion carriers.
 6. Theelectrically variable transmission of claim 1, further comprising afifth torque transfer device connected in parallel with the other ofsaid first and second motor/generators for use in establishing saidfixed ratios.
 7. The electrically variable transmission of claim 6,wherein said fifth torque transfer device is a motor brake.
 8. Anelectrically variable transmission comprising: an input member toreceive power from an engine; an output member; first and secondmotor/generators; not more than first and second differential gear setseach having first, second and third members, wherein said first, second,and third members comprise a ring gear, sun gear, and carrier, in anyorder; and wherein each of said first and second differential gear setsincludes not more than one ring gear, not more than one carrier, and notmore than one sun gear; said input member being continuously connectedwith at least one member of said gear sets, and said output member beingcontinuously connected with another member of said gear sets; aninterconnecting member continuously connecting said first member of saidfirst gear set with said first member of said second gear set, whereinsaid interconnecting member does not connect a sun gear with a carrier;said first motor/generator being continuously connected with a member ofsaid first or second gear set; said second motor/generator beingcontinuously connected with a member of said first or second gear setwhich is different from said member connected with said firstmotor/generator; and first, second, third and fourth torque transferdevices for selectively interconnecting said members of said first orsecond gear sets with a stationary member or with other members of saiddifferential gear sets, said first, second, third and fourth torquetransfer devices being engageable alone to provide an electricallyvariable transmission with a continuously variable range of speed ratiosand in pairs to provide four fixed forward speed ratios between saidinput member and said output member.
 9. The electrically variabletransmission of claim 8, wherein said first and second differential gearsets are planetary gear sets, and said first torque transfer deviceselectively connects a member of said first planetary gear set withanother member of said first or second planetary gear set.
 10. Theelectrically variable transmission of claim 9, wherein said secondtorque transfer device selectively connects a member of said secondplanetary gear set with another member of said first or second planetarygear set, the pair of members connected by said second torque transferdevice being different from the pair of members connected by said firsttorque transfer device.
 11. The electrically variable transmission ofclaim 10, wherein said third torque transfer device selectively connectsa member of said first or second planetary gear set with said stationarymember.
 12. The electrically variable transmission of claim 11, whereinat least one carrier of said planetary gear sets is a double-pinioncarrier.
 13. The electrically variable transmission of claim 11, whereinsaid fourth torque transfer device comprises a motor brake connected inparallel with one of said first and second motor/generators for use inestablishing said fixed ratios.
 14. The electrically variabletransmission of claim 11, wherein carriers of each of said planetarygear sets are single-pinion carriers.
 15. The electrically variabletransmission of claim 11, further comprising a fifth torque transferdevice connected in parallel with the one of said first and secondmotor/generators which is not connected with said fourth torque transferdevice.
 16. The electrically variable transmission of claim 15, whereinsaid fifth torque transfer device is a motor brake.